1. Field of the Invention
The present invention relates to seal structures of valve, and more particularly, to a vacuum valve driven by a linkage structure for sealing the air-tight valve board against the valve opening.
2. Description of the Related Art
In U.S. Pat. No. 7,134,642, a vacuum gate valve, as shown in FIGS. 1a, 1b, and 1c, applies a control unit (such as a hydraulic and rotational unit), such that the valve stem is allowed to move freely along two directions, whereby the valve not only linearly moves along the valve stem axis (in parallel against the valve opening) for covering the valve opening, but also moves in vertical against the valve opening. Thus, when the valve board moves to the valve opening, the valve board is able to produce an addition sealing force upon the valve opening, so as to assure the air-tightness between the valve board and the valve opening.
However, such prior arts usually require a moving track controlling mechanism such as a slide rail disposed at the position of the hydraulic cylinder, wherein different sizes of valve boards and valve openings of vacuum valves with different models or sizes shall be calculated accurately and respectively, such that the valve board is allowed to move to the valve opening and firmly seal the valve opening. Otherwise, if the valve board is unable to cover the valve opening in parallel, the valve board possibly fails to appropriately seal the valve opening. As a result, the air-tightness of the vacuum valve is not achieved. Furthermore, after long period of being repeatedly used, wearing and accuracy deviation of the control unit may occur; in addition, the control unit is usually placed deep in the vacuum valve, causing the difficulty of maintenance.